Filamentary electrode mounting for electronic devices



July 20, 1948. w, STRATTON 7 2,445,411

, FILAMENTARY ELECTRODE MOUNTING FOR ELECTRONIC DEVICES Filed July 50, 1947 FIG. I F/G.Z I

m/ VEN TOR D. S TRA T TON ATTORNEY Patentecl July 20, 1 948 FILAMENTARY ELECTRODE MOUNTING FOR ELECTRONIC DEVICES William D. Stratton, Paterson, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application July 30, 1947, Serial No. 764,622

7 Claims. 1

This invention relates to electronic discharge devices and more particularly to a mounting for a filamentary cathode or electrode substantially in a plane between other cooperating electrodes in a unitary assembly.

An object of the invention is to facilitate as sembly of the filament under tension in a unit mounting.

Another object of the invention is to improve and expedite the anchoring of multiple sections of the filamentary cathode at opposite ends between insulating spacers which support the cooperating electrodes.

A further object of the invention is to equalize the tension strain on the filament sections so that abnormal stresses are avoided.

These objects are attained in accordance with features of this invention by attaching the lower ends of the filament sections to a plurality of clips or formed cantilever metallic punchings mounted in cooperative relation to the suspension springs at the top of the assembly. The multisection filament is uniformly supported in a medial plane between parallel surfaces of cooperating electrodes to provide a mounting assembly in which wide variations in tension strain are eliminated so that greater efliciency and longer life are attained.

A feature of the invention relates to the mounting of the clips in staggered relation upon a spacer to provide rigid arm supports for the individual sections of the filament and to avoid torsional strain on the fine filament strands. This is accomplished, in' one embodiment, by securing a plurality of clips to one side of the spacer to project toward the plane of a quadri-section filament and securing a trio of clips to the other side of the spacer for projecting toward the filament plane, with the free ends of all the clips in alternate relation and opposite the ends of the series sections of the filament. 7

Another feature relates to the formation of the insulator and filament anchor ends of the clips to facilitate the fixation of the respective ends of the clips to the bottom insulator and of the ends and bights of the filament. One end of each clip or anchor is provided with a pair of bent ears to lock the clip in receiving slots in the spacer and the other end is attenuated and bent to form a perpendicular extension having a rightangle .projecting ear or tab in bisecting rela--.

the intermediate sections and the ends thereof to anchor the filament ribbon assembly in the electrode mount. This construction providles a compact assembly in which the multisection filament is rigidly supported so that torsional strains are not imposed on the frail filament to cause displacement out of the axial plane of the cooperating electrodes and the dynamic characteristics of the device are therefore maintained constant. Furthermore, the clips provide rigid anchors which preserve the insulation resistance between adjacent sections so that shorts are eliminated between the sections.

Another feature of the invention is concerned with the reenforcement of the tabs which are attached to the junctions of the filament sections. The tabs extend edgewise from the side of angle portions projecting downwardly from the attenuated end of the clips and therefore the angle base of the tab strengthens the filament anchor to prevent twisting or bending thereof.

A further feature relates to the rigid flat bases of the clips which lie in juxtaposed relation to the spacer plane and are provided with crimping ears for engaging the mica through parallel slots to rigidly afiix the clips to the spacer. This provides a coupling to maintain the clips in constant parallel relation and together with the alternate relation of the clips forms a multidevice involving a filament assembly illustrative of this invention;

Fig. 2 is a view in elevation of the same device as Fig. 1 taken from a different angle to show the related elements of the assembly; in this view the wing spacers of the mount are omitted for the.

sake of clearness;

Fig. 3 is a perspective view of the bottom spacer disc involved in the assembly of the electrode unit or mount with several of the wing supports shown in adjacent relation to the disc and twoof the clips removed from the disc;

Fig. 4 shows in a perspective view the combination of the top and bottom spacers with the multisection filament mounted in position; and,

Fig. 5 is a plan view of the spacer of Fig. 3 taken from the bottom side to show the layout of clips and the coupling of the filament sections thereto.

Referring to the drawing, and particularly to Figs. 1 and 2, the filament supporting assembly illustrative of this invention is shown in a pentode type electrode discharge device in which all the electrodes are held in a unitary assembly or mount and supported in a highly evacuated enclosing vessel. The vessel is composed of a glass bulb or receptacle Ill hermetically sealed to a disc stem l I having a plurality of lead-inwires-or conductors sealed in embossments l 2. The latter are arranged inacircular boundary surrounding a central exhaust tubulation 13 for evacuating and sealing the vessel after the completionof the assembly of the mount therein. The stem is enclosed in a molded insulating base 14 having a plurality of terminal pins or prongs l5 for the accommodation of the electrode conductors or lead-in wires, and the sealed tubulation is protected by a central index projection I6 formed integral with the base.

'The electrode unit or mount supported within the vessel includes a double M-shaped, multisection filamentary cathode l'l surrounded successively by a helical control electrode'or grid IS, a screen grid I0, a suppressor grid and an output electrode or anode 2| of closed box formation and having a joining flange or fin 2'2 projecting from the center of one larger side of the anode. The grids are wound on pairs of support wires or uprights one group of Wires extending through individual holes 23 in the top and bottom insu- :lator spacer discs 24 and 25, preferably of mica, on one side of a'medial plane across the spacer discs and the other wiresextending through a common slot 26 on the other side. The grids are held in accurate spaced relation between the spacer discs by the locking action of the surrounding anode which is provided with bent ears 21 at"opposite'ends,projecting through slots 28 in the discs and bent over on the exterior surfaces of the spacers. Both discs are provided with equally spaced peripheral locking extensions 29 to receive flexible mica wings 30 which engage the inner wall ofthe bulb at their ends, to resiliently support or cushion the mount in the glass vessel. 7

The device is of small size, being shown about twice actual dimensions, so that the electrode mountis proportionally of small dimensions. The filamentary cathode is very frail, being formed in one embodiment of high purity nickel or nickel alloy ribbon .0005 to .0008 inch thickness and .00 2 to ,01 2, inch width and of length to attain the required electron emission for a desired.

power output rating. Such delicate material necessitates extreme carein the assembly of. the electrodes in the unit or mountto prevent damage due to kinks, bends, twists or scraping of, the usualactive coating applied tothe filament surface. Accordingly it is not practical toassemble the filamentary cathode initially in the mount before the other electrodes are placed in positionto insure rigidity to the assembly due to the lack of fixation of the spacers of the mount. On the other hand, prior assemblies created undue welding" difficulties in affixing the filament sections to the supporting elements ifattempts were made to insert the filament after the other electrodeswere placed in'position.

4 In accordance with this invention these difficulties are eliminated and the delicate, fine filamentary cathode may be eiiiciently mounted in the axial plane of the electrodes after such electrodes are aifixed to the spacer discs so that a rigid assembly is assured before the filament is inserted in the mount. This is accomplished by a construction as shown in Figs. 3 1705, inclusive illustrating details of assembly of the filamentary cathode I! between the mica spacers 24 and 25. Although Fig. 4 shows the filament assembled alone between the spacer discs this is only for clarity since'the procedure is preferably reversed, that is the filament is incorporated in the mount after the other electrodes are assembled. Both mica discsare provided with central elongated slots 3! and 32 respectively, the long axis ofeach of which coincides with the medial plane of the other electrodes and extends between the grid holes 23 and the common grid slot 26. These elongated slots provide clearance for the supporting elements of the multisection filament I! and facilitate the insertion of the preformed filament Within the electrodes prior to affixing the mount to the conductors in the stem. The top mica spacer 24 is provided with oppositely disposed pairs of studs 33 mounted in eyelets secured to the spacer disc adjacent'the periphery and parallel to the slot 3|. These studs project vertically from the disc and are arranged in paired relation so that one pair are closetogether on one side and the other pair are spaced wider apart to provide equal spacing between cacti lever type tension springs 3.4 welded to, the ends of the studs. Each pair of springs extend toward the central slot 3i and are provided with downwardly bent hook extensions 35 which are located in the axial plane of the electrodes and extend toward the upper bights of the filament sections, the Widely spaced hooks engaging the. end bights and the closely spaced hooks engaging the intermediate bights of the double M- shapedj filament. The coupling of the filament sections tothej bottom spacer disc 25 in rigid location in theaxial plane of the other electrodes is accomplished by a plurality of metallic fiat clips or punchings which are afiixed to the outer surface of tried [6' and extend in staggered relation towardsthe slot 32 to engage the ends and the intermediatellower big-hts of'the multisection filament array. fllliaich clip is formed the same sothat a description 10f, one will suffice for all, but the group ,of clips are. mounted in opposing relation towards the. s'lotitfd provide uniformity of spacing in relatior'itoi-the tension springs at the top andv tothe folded}sec tions and endsof the filament at thebottom;

The clips are formedof flat metallic strips, as; shown in Fig. 3, having an elongated-wjd m tion 36 and a rstrictednarrow portion 31; 'Op'posite ends of the strips are bent at rightanglesin a downward direction to provide terminal -portions at, and 39, respectively. Each clip includes a pair of upwardly bent ears and a right an gl anchor portion 41 which projects outwardly in edgewise direction from oneside of the terminal portion 39 for securing a section therie-j to. The clips provide rigid securing meanslrcr the lower ends of the filaments, in whiphjtliei wide portion 36 preventstwisting movementv of. the clip, the restricted or attenuated'mifrtionI31;-

insures sufiicient insulation impedance between adjacent anchor portions of theclipsandthe dq nw gd r t te m al se mon. wreenicrces..-

the edgewise anchor 4| projecting outwardly from the clip. .The terminal portion 38 onthe other end of the clip provides a strong base for the attachment or welding of conductors for supplying heating energy to the filament, without being in direct contact with the filament and also facilitates the coupling of the conductors to the filament in the mounting of the unit on the stem of the device. The clips are attached to the lower surface of the spacer 25 by inserting the ears 40 in pairs of short transverse slots 42 and bending the ears over on the other side of the disc toward each other tolock the clips to the spacer disc.

The clips are mounted in two groups on opposite sides of the slot 32 for the specific double M-shaped filament array .11 to distribute the clips in uniform relation withrespect to'the sections of the filament. A trio of clips are afilired to the disc, on one side of the slot 32 and a pair of clips are attached to the other side. The several clips are in alternate lateral relation so that adjacent clips projectfrom opposite directions but coincide in the plane of the lowersurface of the spacer disc. This arrangement causes the anchor portions 4| to bisect the medial plane of the slot, where they are in lateral spaced relation to the sections ofthe filament and since these portions are below the plane of the disc, the filament ends and lower bends therebetween may be readily welded to the portions 4|.

In mounting the ribbon filament in the assembly. the filament, after coating,.is folded in the form of a double M shape and the portions projecting through the lower spacer are scraped to remove the coating so that an efficient weld joint may be performed at the junction with the clip anchors. The preformed filament is inserted through the top slot 3| to project the lower ends toward the clips on the lower spacer. Since the ribbon is fiat it is preferable to mount the sections in edgewise relation to the long dimension of the electrodes so that th fiat sides of the ends and lower sections are parallel to the anchor portions M of the clips. This provides an efficient method of attachment for the filament sections since the scraped ends can be welded to th inside surfaces of the anchors on the end clips of the triple group while the medial bend straddles the anchor of the mid-clip of the same group. In the sam manner, the intermediate bend of each M-shaped section straddles the anchor of the opposite clips and since all these surfaces are in parallel relation and exposed below the spacer disc 25, the welding operation to affix the filament sections to the clips is performed efiiciently and high resistance connections due to defective welding contact are avoided. After the lower ends are attached to the clips, the upper folds or bights of the filament may be positioned by guiding the bends over the stressed hooks until the released hooks impart the necessary tension on the filament sections.

The rigid clip mounting of the lower sections of the filament not only provides an assembly which readily permits the subsequent insertion of the filament in the mount but also facilitates the fabrication of the unit or mount apart from the stem structure. Furthermore, the clips provide a rigid mounting which eliminates torsion strains in the filament sections and, due to the fiat contact of the anchors and the filament bends, removes irregularities in the welded union at these points.

Another advantage of this construction is the manner in which the heatingenergy issupplied to the multisection filament toreduce inequalities in temperature of the sectionsso that variations at the weld joints and in adjacent sections of the filament array are minimized. One method of supplying the energy to the filament is to heat all the sections in series-parallel to provide uniform temperature conditions in all the sections. This is accomplished by tying the triple clips together with a strap wire 43 and connecting the lead-in conductors 44 and 45, respectively, to the pair of clips on the other side of the slot, as shown in Fig. 5. The heating current is then supplied to the .middle junctions of the two M-shaped sections and the current flows in parallel through the sections through the triple tied clips.

When the filament is secured to the conductors in the stem, th anode 2| is connected to conductor 46 which extends through an eyelet in the lower disc and is attached to the fin 22 as by welding. The suppressor grid 20 is connected to conductor 41 by a bridging wire 48 and the screengrid is attached to another conductor in the stem by a tie wire 49, while the control grid respect to a specific assembly of the electrode" mount, it is, of course, understood that various modifications may be made in the detailed assembly of. the elements without departing from the scope and spirit of the invention as definedin the appended claims. 1 r

What is claimed is:

1. An electron discharge device comprising an enclosing vessel, an electrode unit mounted therein including a folded filamentary cathode and a pair of spacer discs on opposite ends of the electrodes having elongated slots therein in line with said cathode, a plurality of tension springs on one disc engaging the bights' of said cathode, a plurality of metallic clips secured to the outer surface of the other disc, said clips having portions projecting across the slot in said other disc, and bent tabs on said portions secured to the ends and intermediate sections of said cathode.

2. An electron discharge device comprising an enclosing vessel, an electrode unit mounted therein including a pair of spacer discs on opposite ends of the electrodes and a multisection filament of folded form extending through aligned slots in said discs, a plurality of tension springs on one side of one of said discs engaging the bights of said filament, a plurality of anchor members secured to the bottom of said other disc and extending toward the slot therein, said members having bent portions located in the plane of said filament, the ends and remaining bights of said filaments being attached to said bent portions, and conductors secured to said members for supplying heating energy to said multisection filament.

3. An electron discharge device comprising an enclosing vessel, an electrode mount therein including a pair of spacer discs at opposite ends of the electrodes and a multisection filament of folded form extending through aligned slots in said discs, a plurality of tension springs on one oflsaid discs engaging therbights .oflsaid filament, a plurality of flat clipssecured'to said'other disc and extending toward the slot therein, said clips having angle bends located in the plane of said filament, the ends and the remaining bights of said filament being attached to said'bendatand conductors connected to said clips.

4. An electron discharge device comprising an enclosing vessel, an electrode mount therein .including aipair of spacer 'discsat opposite ends of the electrodes, and a multi'section filament of folded form extending through aligned slots in said --discs, a plurality of tension springs on one ide'of one of said discs engaging the bights of said filament, a, plurality of flat. clips secured to the other side of the other disc and extending toward the slot therein, said clips having downwardly bentuportions on Opposite ends, means projecting from the, bent-portions adjacent said slot for engaging the folds of said filament sec.- tiQns, and. conductors securedyto the bent portions'disposed away from said slot.

.5. An, electron discharge device comprising an enclosing vessel, an electrode mount therein including a pair of spacer discs at opposite ends of the electrodes. and a multisection filament of folded form extending through aligned slots in said: discs, a plurality of tension springs on one side of one of said discs engaging the bights of said filament, a plurality of fiat metallic clips secured to the bottom of said other disc and extending in opposed relation in alternate :positions toward the slot therein, and edgewise tabs on said clips extending across the central planeofsaid slot, the sections of said; filamentsbeing attached thereto. v

-6. :An electron discharge device comprising; an enclosing vessel, an electrode mount therein including topand bottom spacer discs at opposite ends .ofthe electrodes and a multisection filamentary electrode extending through aligned, central elongated slots in said discs; a plurality oftensicn springs on'said to'p disc engaging the bights of said sections, a plurality of "pairs of transverse slots on opposite sides of said elongatedslotinsaid'bottom disc, a trio of flatclips parallelly extending toward said central slot in said bottom disc, each of said clips having a pair of ears projecting through a related 'pair of transverse slots in the bottom disc and bent over on'the'opposite side ofsaid disc, a pair of similar clips extending toward said central slot in said bottom disc from the opposite direction and mounted in alternate relation with said trio of clips, said similar clips having ears projecting through pairs of transverse slots in the bottom disc and bent overon said disc, and oppositely disposediibent extensions on said clips in the plane of'saidfilainent sections secured thereto to inount said;filamentiassembly in a'central plane between saiddiscs.

"L An-electron discharge device comprising an enclosing vessel an electrode-mount therein ineluding apair of spacer discs at opposite ends of the. electrodes and having central slots therein and 1a doubleiMs-shaped ribbon filament having a plurality oftsections, the fiat-sides thereof being transverse to. the axial plane of said filament, a plurality of staggered metallic clips extending parallel to said disc toward'the central slot in the lower disc, each clipxhaving a downwardly bent portion extending away from said disc and aplurality. of ears projecting through said disc and bent over on the. other side; each clip also having. a restricted portion overhanging the confines of said. slot, the latter portion having a bent terminal part removed from said slot and a transverse edg'eW'isetab. extending across said plane, successive sections of said filament being connected to. alternate tabs of said clips,v and conductors attached to said: downwardly bent portions of said clips.-

D. STRA'I'ION. I 

